Why are novae much more common than supernovae?
A. It takes a special type of white dwarf to go supernova, but any old white dwarf can go nova.
B. Novae are actually brighter than supernovae and so are easier to find.
C. A white dwarf's mass slowly decreases with each nova but the whole white dwarf is completely obliterated during a supernova
D. Both B and C
E. None of the above
Ans: C. A white dwarf's mass slowly decreases with each nova but the whole white dwarf is completely obliterated during a supernova
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An electron is confined in a one-dimensional box (an infinite well). Two adjacent allowed energies of the electron are 1.068 × 10-18 J and 1.352 × 10-18 J. What is the length of the box? (h = 6.626 × 10-34 J ? s, mel = 9.11 × 10-31 kg)
A) 0.93 nm B) 1.1 nm C) 2.3 nm D) 1.9 nm
Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around massive black holes?
A) The total amount of radiation coming from the galactic center can, in some cases, exceed 100 times the total luminosity of the Milky Way Galaxy. B) Infrared observations show that many stars are forming near the centers of active galaxies. C) Observed radiation from the galactic center can vary significantly in brightness in times as short as a few days. D) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed. E) Radio observations sometimes show long jets of material that can extend millions of light-years out from the galactic center.
What is the ultimate fate of an isolated white dwarf?
A) It will cool down and become gradually dimmer. B) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova. C) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova. D) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star. E) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly evaporate.
A magnetic field is applied to a cloud chamber for the purpose of
A) attracting electrons. B) repelling electrons. C) attracting protons. D) all of the above E) none of the above